Oh!!! I hadn't thought of that Gretchen, that might be it, because it has boiled over about 6 times now and I havent topped the oil up, because I worked on the logic that less oil means it's less likely to boil over, so it's probably gone below the minimum indicator now.

I'm not clear what you mean by "topped up th e oil". I think it is fairly certain if your oil is always boiling over that you are putting too many potatoes into to small an amount of oil. Try using half the amount of potatoes you have been using in the oil. The oil should only be approximately half way up the side of the cooker.
It has MUCH less to do with the type of potato (although it should NOT be a waxy style like "new" potatoes) or the moisture on the potato (but you should blot them dry). It about has to have to do with volume.

Was your oil pretty fresh - old oil will foam up I think. Just add a few chips at a time (That has been patted dry) and see how they do --hope your oil isn't too hot - for your first fry. Good luck and keep us posted-

The only time I've had that problem has been when there's been too much moisture involved. Is the deep fryer completely dry when you add the oil, is the basket completely dry???????

Does this happen when you deep fry other foods??????

You might try putting a few TBS of cornstarch in a bag - with some seasonings? - and shake the chips in the cornstarch before adding them to the hot oil. I've had chips cooked this way and they are amazingly crisp!

Soaking vs Rinsing: This is only necessary for one of two reasons (1) you're cutting your tatties in advance and want to prevent oxidation or (2) you want to remove the surface starch so they will not get as brown as they will if you don't wash off the surface starch. I cut mine right when I am ready to use them (not soaking or rinsing) and no problems.

Moisture: Regardless of whether you soak, rinse, or just cut-and-fry - potatoes contain moisture inside - not just on the surface. Blotting the moisture from the surface of the potatoes will help reduce spattering and sputtering from surface moisture ... but it has no affect on the internal moisture. As you lower the basket into the fryer the moisture in the potatoes expands and escapes (the oil is at a temperature in excess of the boiling point of water) and it is the pressure exerted by the water in the potatoes that keeps them from absorbing oil!

Double Fry Method: The only reason to fry twice is to get a tender interior and a crunchy golden exterior. 150&#186;C for 5-8 minutes, remove and allow them to cool on a rack to room temp (or at least 10 minutes) and then fry the second time for 2-4 minutes at 185&#186;C will probably work best.Of course, the initial fry time depends on how you cut your tatties - are you making French Fries (square cross-section) or English chips (wedges)?

Boiling Over: It's a matter of the total volume of the fryer, volume of the oil, volume displacement (from the amount of food you put into it), oil temperature and water content. Your fryer should have a minimum and maximum oil level mark - as long as your oil level is somewhere between those marks you should not have a problem caused by the oil level.

Method: This goes back to what Andy M. said .... lower the food in the basket into the oil "slowly" - and if it starts to boil up too quickly - pull the basket back up out of the fryer for a couple of seconds, then lower it again - repeat as necessary until when you have the basket lowered all the way into the fryer and it doesn't "boil over". You can take frozen foods directly out of a bag (with ice crystals on them) and stick them into a deep fryer without "boil-over" if not too much is introduced at one time.

Read the Instructions: Read the instructions that came with your fryer, and follow them. I went out and looked at the User's Manuals for several modern brands of home fryers- they pretty much all said what I just said.

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"It ain't what you don't know that gets you in trouble. It's what you know for sure that just ain't so." - Mark Twain

last night I completely emptied the fryer and re-filled it with fresh oil and to my relief it didn't boil over, the oil bubbled nicely, but didn't "foam" up to the golden yellow colour it did before.

I hope this is problem solved, although I don't understand why it did it from the day I bought the fryer and put the first lot of oil in, the only thing I can think of is, maybe when I unpacked the fryer and washed it before first use, I didn't dry it thoroughly enough. Lesson learned.

Thanks for all your help, as well as useful advice, I've got some good tips on cooking the perfect chip in this thread and it has lead me to find this forum which I think is great.